MICROBIAL-DEGRADATION OF SORBED AND DISSOLVED PROTEIN IN SEAWATER

The effects of adsorption and concentration on rates of protein degrad ation by marine bacteria were examined by measuring hydrolysis and rem ineralization of the radiolabeled protein, ribulose-1,5-bisphosphate c arboxylase-oxygenase ([methyl-H-3]Rubisco). Protein adsorbed at low su rface concentrations on glass beads had hydrolysis and remineralizatio n rate constants 247% and 282% higher than protein bound at high surfa ce concentrations. Moreover, thin films of bound protein were hydrolyz ed and remineralized 522% and 1,033% faster than comparable pool sizes of dissolved protein. At high concentrations, however, rates of hydro lysis and remineralization were not significantly different between pr oteins in dissolved or sorbed pools. Results demonstrate that proteins adsorbed to surfaces can be as bioavailable as those in solution. In fact, the sorption process may actually aid bacterial degradation by c oncentrating the protein and hydrolysates at an interface and by unfol ding proteins to relax steric hindrance and expose a higher proportion of bonds to bacterial endo- and exohydrolases.